Channel Config: Setup Internal Signal Conditioning

The signal conditioning settings available on each channel will depend on the hardware fitted. The dragonfly acquisition card can be coupled with various flavors of signal conditioning.

The signal conditioning settings are editable in the “Sig Cond” tab of the channel configuration screen.

The primary setting is the gauge type, as show above. The gauge type is a drop down list; the gauge types available are the intersection of:

  • The gauge types supported by the signal conditioning hardware fitted on that channel
  • The gauge type allowed for the channel type (Channel Type has been specified in the main tab). That is defined in the Preferences Unit page.

Gauge Type Definition

The graphic below shows how to define the allowed gauge type for a given channel type, in the preferences:

Step 1, select the Unit tab

Step 2, select the channel type

Step 3, click on the gauge types button

Step 4, select the gauge type; up to 5 gauge types can be ticked for a given channel type.

The different gauge types available are described in the table below:

Gauge type

Description

Settings available (if supported by hardware)

Default

Deprecated

 

This will not be available as a gauge type in the “Channel Config” “Sig Cond” tab.

Static Strain ¼ Bridge

¼ bridge static strain gauge

·       Gain

·       Bridge supply type (current, voltage) and value

·       AC/DC Coupling

·       Bridge Completion resistor (¼ bridge only)

·       Bridge balance resistor + Auto-zero

·       Shunt resistor + shunt calibration signal

·       Output calibration signal

·       Local / remote sense (for ½ and full bridge)

·       Filter

Static Strain ½ Bridge

½ bridge static strain gauge.

Static Strain Full Bridge

Full bridge static strain gauge.

 

For Kulites, the user will use Full Bridge, Voltage Excitation, DC Coupling.

Dynamic Strain

Dynamic strain gauge.

·       Gain

·       Current supply value

·       AC coupling with configurable high pass filter

·       Calibration voltage injection

·       Compliance voltage

 

Accel ICP

ICP accelerometer

·       Gain

·       Current supply

·       AC coupling with configurable high pass filter

Accel Charge Differential (Sym.)

A differential / symmetric charge accelerometer

·       Gain

·       AC coupling with configurable high pass filter

Accel Charge Single Ended (Asym.)

Single ended / asymmetric charge accelerometer

Voltage

Voltage gauge

·       Gain

·       AC/DC Coupling with configurable high pass filter for AC coupling.

·       Filter

·       Single ended / differential

Prox probe

Bently Nevada TM Proximity probe

·       Gain

·       DC Offset

Photo sensor

Photo sensor

·       Gain

Channel Signal Conditioning Settings

The first step is to choose a gauge type.  Depending on the gauge type selected and the conditioning fitted on the channel, some of the settings will be enabled.

In the example below, we have a dragonfly with IEPE + VOLTAGE capabilities, so the only gauge type available for a channel of type “ACCEL” is “ACCEL ICP.”

Then we can distinguish 3 types of settings:

  • The settings that are non-applicable are greyed out.
  • Some settings such as the coupling have been forced to the only value that makes sense (Figure 60).
  • For other settings such as the gain, the user has a choice (Figure 61).

IMPORTANT: it is possible to setup a configuration in advance, without any hardware available. In this case, the settings available, and the possible values for those settings will be worked out based on all the various hardware supported by HGL acquisition system.

In the example below, we have disconnected our dragonfly IEPE + voltage and flushed the devices, so no hardware is mapped to channel 2.

The list of possible gain values now goes beyond 200, because some of the signal conditioning hardware provided by HGL does so.

We now connect the dragonfly back into the test cell; the gain of 2000 previously chosen is displayed in red because it is not supported by this specific hardware.

When the user wants to change it, the list is again displayed restricted to only the values for which the hardware supports (so up to 200 in this case). 

Select a gain of 200 and the cell is no longer red.

Internal/External Signal Conditioning

There are 2 tabs in the signal conditioning page, called internal and external, as shown below:

Internal conditioning is embedded on the acquisition card; external conditioning is a separate signal conditioning rack. Different hardware configurations are possible:

  • No conditioning, in this case the system only accepts voltage input
  • Internal conditioning fitted on the dragonfly card
  • External conditioning rack, before the acquisition card in the signal path
  • External conditioning and internal conditioning together

In this last case, the internal conditioning may be used for gain only, and the external conditioning will be used to its full capability, and will convert the sensor output into voltage.

That can be setup on a per channel basis, as show below:

Once “gain only” has been selected, every setting but the gain will be disabled. The user can then move on to the external tab to setup the external signal conditioning on the channel.

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